Eficiência de estação de tratamento de esgoto doméstico visando reuso agrícola/Efficiency of domestic wastewater treatment plant for agricultural reuse

The increasing demand for water has made the treatment and reuse of wastewater a topic of global importance. This work aims to monitor and evaluate the efficiency of a wastewater treatment plant's (WWTP) physical and biological treatment of wastewater by measuring the reduction of organic matter content of the effluent during the treatment and the disposal of nutrients in the treated residue. The WWTP has been designed to treat 2500 liters of wastewater per day in four compartments: a septic tank, a microalgae tank, an upflow anaerobic filter and wetlands with cultivation of Zantedeschia aethiopica L. A plant efficiency of 90% of organic matter removal was obtained, resulting in a suitable effluent for fertigation, including Na and Ca elements that showed high levels due to the accumulation of organic matter in the upflow anaerobic filter and wetlands. The WWTP removes nitrogen and phosphorus by the action of microalgae and macrophytes used in the process. The final effluent includes important agricultural elements such as nitrogen, phosphorus, calcium and potassium and, together with the load of organic matter and salts, meets the determination of NBR 13,969/1997 (Standard of the Brazilian Technical Standards Association) for reuse in agriculture, but periodic monitoring of soil salinity is necessary.